notable changes:
struct spng_decoder -> struct spng_ctx
spng_decoder_set_buffer/stream() -> spng...

be32tou, be16tou -> read_u32, read_u16
added read_i32() function

Use be{16,32}tou instead of ntoh[sl] to solve issue #2

See merge request randy408/libspng!2

Passing "info" as first argument will print spng and libpng
version information and exit.

Invalidate decoder state so that subsequent calls fail early.

Replace inappropriate use of %u with PRIu{8,16,32} macros

See merge request randy408/libspng!3

%u is not a portable solution for printing fixed width types. Even in
the current code default a...

before set_stream() was added IHDR was read when set_buffer() was
called, this is no longer the ...

testsuite: for gamma-corrected images each channel of a pixel is
checked to be within 2% of libp...

also fixed some error codes being assigned to the same number

Split next_chunk() into next_header() and get_chunk_data()
IDAT chunks are read up to chunk.leng...

Removed 16-bit sample endianness workaround
Removed PNG output format
Default behavior changed t...

Added a compile-time option that disables conversion to host
endianness for 16 bit samples, this...

libspng = simple png library,
the "v" in vpng didn't stand for anything, it was added to avoid
n...

vpng_get_image_rgba8() -> vpng_decode_image()
vpng_decode_image() has two more args: output form...